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openssl_cipher_iv_length

(PHP 5 >= 5.3.3, PHP 7)

openssl_cipher_iv_lengthObtener la longitud del iv de cipher

Descripción

int openssl_cipher_iv_length ( string $method )

Obtiene la longitud del vector de inicialización (iv) de cipher.

Parámetros

method

El método de cipher, véase openssl_get_cipher_methods() para una lista de valores potenciales.

Valores devueltos

Devuelve la longitud de cipher en caso de éxito, o FALSE en caso de error.

Errores/Excepciones

Emite un error de nivel E_WARNING cuando el algoritimo de cipher es desconocido.

Ejemplos

Ejemplo #1 Ejemplo de openssl_cipher_iv_length()

<?php
$método 
'AES-128-CBC';
$longitud_iv openssl_cipher_iv_length($método);

echo 
$longitud_iv;
?>

El resultado del ejemplo sería algo similar a:

16
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User Contributed Notes 2 notes

up
7
Tim Hunt
3 years ago
The return value is a length in bytes. (Not bits, or anything else.)
up
0
Vee W.
18 days ago
<?php
$ciphers
= openssl_get_cipher_methods();

//ECB mode should be avoided
$ciphers = array_filter($ciphers, function ($n) {
    return
stripos($n, "ecb") === FALSE;
});
   
// At least as early as Aug 2016, Openssl declared the following weak: RC2, RC4, DES, 3DES, MD5 based
$ciphers = array_filter($ciphers, function ($c) {
    return
stripos($c, "des") === FALSE;
});
$ciphers = array_filter($ciphers, function ($c) {
    return
stripos($c, "rc2") === FALSE;
});
$ciphers = array_filter($ciphers, function ($c) {
    return
stripos($c, "rc4") === FALSE;
});
$ciphers = array_filter($ciphers, function ($c) {
    return
stripos($c, "md5") === FALSE;
});

if (
is_array($ciphers)) {
    foreach (
$ciphers as $cipher) {
        echo
$cipher.': ';
        echo
openssl_cipher_iv_length($cipher);
        echo
"<br>\n";
    }
}
?>

Will be...
AES-xxx-xxx is 16
BF-xxx is 8
CAMELLIA-xxx is 16
CAST5-xxx is 8
IDEA-xxx is 8
SEED-xxx is 16

lower case:
aes-xxx-xxx are mixed between 16 and 12.
id-aes-xxx are mixed between 12 and 8.
The values above are tested with PHP 5.5 - 5.6 on Windows. In PHP 7.x is different than this.
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